1. Technical Field
The present invention relates to a developing roller, a toner and an image forming apparatus.
2. Description of the Related Art
An image forming apparatus using one-component contact developing method provides a toner from a rotating developing roller on the surface of which a toner thin layer is formed to an electrostatic latent on the surface of a photoconductor to form a toner image. It is known that the toner thin layer is formed by a regulation blade (regulation member).
Since the one-component contact developing method strongly frictionize a toner with the regulation blade to charge the toner, a large stress is given to the toner. Therefore, the method is not suitable to a low-temperature fixable toner which is the recent mainstream. Particularly, toner anchorage on the regulation blade and toner filming on the developing roller are likely to be caused. This is partly because a toner is strongly frictionized by the regulation blade and a temperature therearound increases to soften toner components such as a wax (release agent) and a fixing assistant, resulting in adherence thereof to the regulation blade.
This causes adherence of the toner itself, an external additive thereof, etc. to the regulation blade or the developing roller, and the adherence expands due to stress, resulting in the anchorage on the regulation blade and the filming on the developing roller. The anchorage on the regulation blade disturbs passage of a toner through a nip of the regulation blade, resulting in image void. The filming quicken deterioration in quality of the developing roller as time passes, resulting in lowering of charge quantity, increase of toner consumption due to deterioration of background fouling, and deterioration of solid image followability due to lowering of scrapability.
The toner anchorage on the regulation blade and the toner filming on the developing roller have a trade-off relation, and it has been difficult for conventional developing rollers to solve the two problems at the same time. Developing spheric polymerization toners having good low-temperature fixability, and further high-speed printing and long-life image forming systems noticeably have these problems.